/*********************************************************************
 * Copyright (C) 2002 Andrew Khan
 * <p>
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p>
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * <p>
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ***************************************************************************/

package jxl.write.biff;

import jxl.biff.IntegerHelper;
import jxl.biff.Type;
import jxl.biff.WritableRecordData;

/**
 * A password record.  Thanks to Michael Matthews for sending me the
 * code to actually store the password for the sheet
 */
class PasswordRecord extends WritableRecordData {
    /**
     * The password
     */
    private String password;
    /**
     * The binary data
     */
    private byte[] data;

    /**
     * Constructor
     *
     * @param pw the password
     */
    public PasswordRecord(String pw) {
        super(Type.PASSWORD);

        password = pw;

        if (pw == null) {
            data = new byte[2];
            IntegerHelper.getTwoBytes(0, data, 0);
        } else {
            byte[] passwordBytes = pw.getBytes();
            int passwordHash = 0;
            for (int a = 0; a < passwordBytes.length; a++) {
                int shifted = rotLeft15Bit(passwordBytes[a], a + 1);
                passwordHash ^= shifted;
            }
            passwordHash ^= passwordBytes.length;
            passwordHash ^= 0xCE4B;

            data = new byte[2];
            IntegerHelper.getTwoBytes(passwordHash, data, 0);
        }
    }

    /**
     * Constructor
     *
     * @param ph the password hash code
     */
    public PasswordRecord(int ph) {
        super(Type.PASSWORD);

        data = new byte[2];
        IntegerHelper.getTwoBytes(ph, data, 0);
    }

    /**
     * Gets the binary data for output to file
     *
     * @return the binary data
     */
    public byte[] getData() {
        return data;
    }

    /**
     * Rotate the value by 15 bits.  Thanks to Michael for this
     *
     * @param val
     * @param rotate
     * @return int
     */
    private int rotLeft15Bit(int val, int rotate) {
        val = val & 0x7FFF;

        for (; rotate > 0; rotate--) {
            if ((val & 0x4000) != 0) {
                val = ((val << 1) & 0x7FFF) + 1;
            } else {
                val = (val << 1) & 0x7FFF;
            }
        }

        return val;
    }
}
